1. Technical Field
The present invention relates to semiconductor processing and more particularly to fabrication of components where multiple widths are formed simultaneously.
2. Description of the Related Art
Vertically disposed transistors formed on fins or fin field effect transistors (FinFETs) have been emerging as a promising new approach for continued scaling of complementary metal oxide semiconductor (CMOS) technology. Sidewall spacer imaging transfer (SIT) is one method for forming narrow fins beyond the printing capability of optical lithography. Conventional SIT methods result in fins with a same width across the chip. Some applications, however, require fins with different widths on the same chip. For example, various finFET devices on the same chip may require different fin widths for different threshold voltages. In another example, finFET devices may be formed on the same chip with other devices such as tri-gate devices or planar devices which require different fin widths from the fin width for finFET devices.
U.S. Pat. No. 6,492,212 employs an extra mask 215 to cover some spacers while exposing and trimming other spacers. However, this requires many lithographic steps and increased process complexity, cost, non-uniformity, overlay issues, defect magnification by spacers, etc. While U.S. Pat. No. 6,492,212 discloses a method for forming fins with different widths by using sidewall spacer imaging transfer, after forming the sidewall spacers 214 on dummy mandrels 212, an extra mask 215 is used to cover spacers in some regions while exposing spacers in other regions. Spacers not covered by mask 215 are then trimmed to a thickness less the spacer thickness is covered by the mask 215. U.S. Pat. No. 6,492,212 requires an additional mask for each variation of fin width. For example, three additional masks are needed in order to form fins with four different widths. Additional masks not only add process complexity, but also increase process cost. Moreover, this method introduces non-uniformity issues (e.g., variability in spacer trimming, different spacer heights after some spacers are trimmed, overlay issues, etc.).
U.S. Pat. No. 7,265,059 also involves process complexity and cost, severe defect magnification by spacers, etc. U.S. Pat. No. 7,265,059 discloses another method for forming fins with different widths by using dual spacers. Dual spacers 315 and 417 are formed. The spacer 315 is then removed, leaving a narrow pattern 417 and a wide pattern 209 for forming fins with different widths. The two spacer process adds complexity and increases process cost. Moreover, the ‘defect magnification’ issue in spacer imaging transfer process is more severe due to the two spacer process.